1. Technical Field
The present invention relates to a motor drive device including a drive circuit for driving a motor, and a control section for controlling the drive circuit.
2. Related Art
A motor drive device 500 including an inverter 510 for driving a motor 550, and a control section 520 for controlling the inverter 510, as shown in FIG. 14, is conventionally known. This motor 550 is, for example, a three-phase brushless motor.
The inverter 510 generates a drive current of three phases based on a PWM signal inputted from the control section 520. The inverter 510 drives the motor 550 by outputting the drive current of three phases to the motor 550.
The control section 520 includes a current command value calculating portion 521, a rotation calculating portion 522, a current actual measurement value calculating portion 523, a voltage command value calculating portion 524, and a drive signal generating portion 525.
A current command value Iref is inputted to the current command value calculating portion 521, so that the current command value calculating portion 521 calculates a d-axis current command value Ir_d and a q-axis current command value Ir_q based on the current command value Iref. The current command value calculating portion 521 then outputs the d-axis current command value Ir_d and the q-axis current command value Ir_q to the voltage command value calculating portion 524.
The rotation calculating portion 522 calculates a rotation angle θ of the motor 550 based on a detection signal of a resolver 551 for detecting a rotation angle of the motor 550. The rotation calculating portion 522 outputs the rotation angle θ to the current actual measurement value calculating portion 523 and the drive signal generating portion 525.
The current actual measurement value calculating portion 523 calculates current actual measurement values Iu, Iv, Iw of each phase flowing to the motor 550 based on the detection result of the current detection portion 511. The current actual measurement value calculating portion 523 converts the current actual measurement values Iu, Iv, Iw to d-axis current actual measurement value If_d and q-axis current actual measurement value If_q using the rotation angle θ of the motor 550 calculated by the rotation calculating portion 522. Thereafter, the current actual measurement value calculating portion 523 outputs the d-axis current actual measurement value If_d and the q-axis current actual measurement value If_q to the voltage command value calculating portion 524.
The voltage command value calculating portion 524 calculates a d-axis voltage command value V_d based on the d-axis current command value Ir_d inputted from the current command value calculating portion 521 and the d-axis current actual measurement value If_d inputted from the current actual measurement value calculating portion 523, and also calculates a q-axis voltage command value V_q based on the q-axis current command value Ir_q inputted from the current command value calculating portion 521 and the q-axis current actual measurement value If_q inputted from the current actual measurement value calculating portion 523. The voltage command value calculating portion 524 then outputs the d-axis voltage command value V_d and the q-axis voltage command value V_q to the drive signal generating portion 525.
The drive signal generating portion 525 converts the d-axis voltage command value V_d and the q-axis voltage command value V_q inputted from the voltage command value calculating portion 524 to application voltage values Vu, Vv, Vw of three phases using the rotation angle θ of the motor 550 calculated by the rotation calculating portion 522. The drive signal generating portion 525 then generates a PWM signal (PWMu, PWMv, PWMw) for driving the inverter 510 based on the application voltage values Vu, Vv, Vw of three phases.
When such a conventional motor drive device 500 drives the motor 550, the inductive voltage of the motor 550 is desirably a sinusoidal wave. However, the inductive voltage of the motor 550 has a drawback in that torque ripple and abnormal sound occur since a harmonic wave is superimposed on the fundamental wave.
In the prior art, a motor drive device including a current command value correcting portion for suppressing the occurrence of torque ripple and abnormal sound has been proposed (see e.g., Japanese International Patent Publication WO 2005/081397 and Japanese Unexamined Patent Publication No. 2006-288076).
Japanese International Patent Publication WO 2005/081397 discloses a motor drive device including a current command value correcting portion that receives a q-axis current command value from a current command value calculating portion and receives a rotation angle of the motor from a rotating calculating portion. Such current command value correcting portion adds a correction value corresponding to the rotation angle of the motor to the q-axis current command value and outputs the q-axis current command value added with the correction value to the voltage command value calculating portion.
Japanese Unexamined Patent Publication No. 2006-288076 discloses a motor drive device including a current command value correcting portion that receives a d-axis current command value and a q-axis current command value from a current command value calculating portion, and receives a rotation angle of the motor from a rotation calculating portion. Such current command value correcting portion corrects the d-axis current command value and the q-axis current command value based on the rotation angle of the motor and a parameter of the motor. The current command value correcting portion outputs the corrected d-axis current command value and the q-axis current command value to a voltage command value calculating portion.